Hello.

In our new kitchen I am having electric mat UFH installed under tiles over about 17m squared area. Its primary role was to be 'under foot' cosyness but at 150w/m squared rating I also would expect it to do some heating duties. Electric was chosen by the way as we are on a tight budget.

Question 1 – How many BTU's does 17m squared of a 150W mat put out please and how do I work that out?

I am now hoping to do a bit of 'half and half'. The kitchen is biggish and needs about 9000 BTU's. I was going to buy about 4500 BTU's in two rads as I thought it a good idea to have two heating methods and its good for drying socks! I would leave the other 4500 BTU's to the UFH. I could buy 9000 BTUS of Radiator power but we want 'designer' rads and they aint cheap.

Will the half and half approach work?

The TRV on the rad will look after thermostatic duties I assume and the floor thermostat in the UFH will keep the floor temp steady?

Is 150W big enough or do I need 200W for what Im trying to do?

Last question. I understand that I need to buy some underboard insulation to go on top of the concrete and under the mat to help efficiency.
Is it worth going for stuff like Kilma at £26/ meter squared which seems very expensive at £500 for the room or can I get something more reasonable?

It's not rocket science and its not life or death but I do want to get the in the right ball park.

Any help welcome!! Best Regards, Scott

bump 🙂

Can't help on the BTU or capacity ratings but I used Warmup loose cable in our kitchen and most of the year it copes fine without a radiator to keep the place warm. I just sized it using the standard tables on their website.

I did use some insulating board, again it was the warmup stuff that I got for a good deal with the heating cable, but can't remember how much it was, pretty sure it wasn't cheap though – from this place it looks like about £300 for 17 m2 clicky .

It is noticeable the floor warms up very quickly and insulation can only be a good thing.

Hope that is of some use.

Second vote for the Warmup system.

We have this in a porch under fairly thick tiles.
The controller has different settings for the type of flooring and over the last year has worked brilliantly. Particularly good for wet outdoor gear, which we spread over the floor to dry it out.

Can't comment on all the technical details however their technical support people were brilliant when I called them, so may be worth a try.

a lot depends on the U value of the room you are heating and the insulation of the floor but

17mtrs square = 2250 Watts

so 2250 Watts per second = 2.13259 BTU

Ibis – where on earth did you get that figure from?

2250 watts = 7677 BTU.

Not worked with electric underfloor, but have heard that it can be expensive to run.

the conversion factor is 3.412BTU = 1watt, so you have 8700BTU.

however, electric is the most expensive fuel at present, so bear is correct that it is relativly expensive to run, compared to the rest of your house, which I assume is gas or oil.

They do work well however, and assuming the kitchen is not too old, 150W/msq should be enough output – modern builds require no more than 50W/msq and some as low as 20-25.

Hope this helps.

Why did you discount wet ufh? A 20 sqm polyplumb kit is around 220 quid. Wet will work much more efficiently and give a huge output.
A 17 sqm warmup kit will be around 400, plus much higher running costs

Thanks. I know ST forum wouldnt let me down..

So does the bidding end at 8700 BTU? 🙂

The room area is not 17m squared – that would be the matting area. Room is 25 m sq and has high lofted ceilings (average height of about 2.8m) and large patio doors + four velux. Its a modern build (new extension) so the 9000 BTU is from me going on taking an average of four online calculators and adding a 10 percent safety margin! I know they are not fantastic but what else do I do – employ a professional!!!??? 😉

So its debatable if I need the additional rad I guess. Will probably still go with just in case I my toes start to curl or something.

I didn't realise wet systems were so cheap to install. Funkymonkey – is £220 for a full kit including all controls etc? Ar ethey suitable for combis? I know they are cheaper to run. Ill definately have a look at that option now.

Any other gems of knowledge? Again all help welcome.

Scotster.

try the stars program from stelrad to size the heat loss [ its free…..]

Clicky

should be fairly self explanatory to use. get the heat loss, speak to Uponor or Polypipe and look at the small area packs. I'd be suprised if you get it for £250 but no harm in researching. bear in mind that the price doesnt include the insulation or the screed.